Previous results from several laboratories have indicated that the pp65 tegament protein from CMV is the major immunogenic protein recognized by individuals who are seropositive for the virus. CTL clones, which recognize pp65 in the context of ten different HLA Class I alleles, have been identified by our alboratory. The repertoire of epitopes that have been defined for these clones are representative of approximately 95% of the ethnic population of the United sates. Evaluation of whether these CTL epitopes are predominantly used in the general population requires an analysis of the immunogencity of the approach of stimulating peripheral blood lymphocytes form HLA-typed individuals who are seropostive for CMB, in a techique in which the free peptide epitope is added at a high concentration to PBMC in mictowell cultures. We have used this approach with CTL eptiopes specific for pp65 and restricted by HLA A*0201, A*1101,A*2402,A*6901 and B*0702. In each case, we have examined less than five healthy volunteers who are seropositive and hve been shown to respond to the CTL epitopes that are specific for the the HLA allele, which they ecpress. CD8+CTL, which recognize both peptide loaded and CMB infect targets, are amplified 100-foold in a two-week period. The use of the in vitro stimulation procedure allows a sensitive determination of whether an individual is making a CTL response to CMB, and whether pp65 is a component of that response. We wish to demonstrate that a t least five, and ifpossible, ten randomly chosen individualts will respond to a single epitope, suggesting the potential for a universal response to that epitope forma ll individuals who express the same restricting Class I allele. This provides the rationale for an approach to producing vaccine molecules, containing one or more of these epitopes to immunize at risk individuals against CMV infection. The clinical procedures of obtaining both peripheral blood and biopsy are the central part of the lcinical protocol, and could be best carried out under the auspices of the GCRC. We have developed cohorts fo individuals who express the HLA alleles for which we have epitopes form pp65, and more recently, pp150. We wish to carry out these studies, to characterize all of the major eppitopes of CMV pp65 and pp150, which are improtant in the juman immune reaponse to the virus. The prpose for carrying on these studies is to define a peptide-based vaccine that would be applicable to all at-risk individuals. we wil also continue to derive new CMV epitopes, to complete our repertoire of epitopes that would ensure as complete a representation as possible of individuals of different ethnicities that make up the american population. There are several consent forms (A-D) which are active for the protocol.